Not sure this is the cause, but I define the DescriptionAttribute, not the Description, as you are coding over there:
''' <summary>''' Define the color used to highlight items that have passing''' scores.''' </summary><Category("RAMS: Score Formatting") _ , DescriptionAttribute("Define the color used to highlight passing scores in the list.")> _Public Property PassingBackColor() As Color Get Return _passingBackColor End Get Set(ByVal value As Color) _passingBackColor = value End SetEnd Property